1. Field of the Invention
The present invention relates to a structure of a battery holder for use in backing up a memory in various electronic devices including game software and office machines, and more particularly to a housing structure for a flat battery.
2. Description of the Related Art
The structure of a battery holder for a flat battery according to the prior art is illustrated in FIG. 14 through FIG. 16. FIG. 14 is a plan of the battery holder; FIG. 15, a sectional view along a line 15xe2x80x9415 in FIG. 14; and FIG. 16, a perspective view of the battery cut along the line 15xe2x80x9415 in FIG. 14.
Referring to the drawings, a case 31, consisting of an insulator such as a synthetic resin, is formed in a substantially cylindrical shape with an opening at the top. In this case 31 are provided a bottom plate 31a to meet one face of a flat battery 32 and a peripheral wall 31b to meet this battery 32, and at its top is arranged an opening 31c through which the battery 32 is to be inserted. At one end of the peripheral wall 31b is provided a notch 31d, and opposite this notch 31d is arranged, inside the peripheral wall 31b and in contact with the peripheral face of the inserted battery 32, a first terminal 33 having elasticity to press this battery 32 toward the notch 31d. Inside the bottom plate 31a is arranged a second terminal 34 in contact with one face of the battery 32. Toward the upper end of the peripheral wall 31b where the notch 31d and the first terminal 33 are provided, protruding barriers 31e and 31f to prevent the battery 32 from coming off from the opening 31c are arranged to suppress the upper face of the battery 32 inserted through the opening 31c. 
The first and second terminals 33 and 34 are formed of plates of springy metal, such as stainless steel, and nickel-plated or otherwise appropriately treated on the surface. The first terminal 33 is provided with a pair of first contacts 33a arranged within the peripheral wall 31b of the case 31 and in contact with the peripheral face (the positive pole face) 32a of the flat battery 32, while the second terminal 34 is provided with a second contacts 34a arranged within the bottom plate 31a of the case 31 and in contact with the bottom face (the negative pole face) 32b of the battery 32. One end each of the first and second terminals 33 and 34, protruding out of the case 31, is connected to the conduction pattern (not shown) of a printed circuit board 35.
Then, to house the flat battery 32 in the battery holder, after mounting the battery holder on the printed circuit board 35 and soldering the first and second terminals 33 and 34 on the conduction pattern (not shown), the battery 32 is inserted in a slanted state into the case 31 through its opening 31c. During this action, the battery 32 is engaged by the protruding barriers 31e and 31f provided toward the upper end of the peripheral wall 31b, and its bottom face (the negative pole face) 32b is held by being in contact with the second contact 34a arranged on the bottom plate 31a, and the peripheral face (the positive pole face) 32a of the battery 32 is housed in the case 31 by being in contact with the paired first terminals 33a. 
However, in the conventional battery holder structure for the flat battery described above, the protruding barriers 31e and 31f for preventing the battery 32 from coming off are formed toward the upper end of the peripheral wall 31b of the case 31, and the battery is inserted in the slanted state into the opening 31c of the case 31 to have the battery engaged by these protruding barriers 31e and 31f. Therefore, considering the ease of inserting the battery, it is impossible to form the protruding barriers 31e and 31f in too large a size, and this makes it impossible to engage the battery 32 so firmly, resulting in the problem that any vibration or impact from outside may cause the battery 32 to spring out of the case 31 or its contacts to become momentarily disconnected to let the power supply go off.
An object of the present invention, therefore, is to solve the above-noted problem and to provide a battery holder for a flat battery which, when a flat battery is to be inserted into the battery holder, allows the battery to be easily inserted and held firmly to prevent it from springing out or its contacts from becoming disconnected when any vibration or impact from outside is suffered.
In order to achieve the object stated above, according to a first aspect of the invention, there is provided a battery holding section comprising a bottom plate meeting one face of a flat battery, a peripheral wall meeting the peripheral face of the battery, a case having in its top face an opening through which the battery is to be inserted, and first and second terminals, arranged within this opening of the case, to be in elastic contact with the poles of the battery, wherein protruding barriers are formed toward one end of the opening in the case to engage with the top face of the inserted battery to prevent the battery from coming off, and elastically deformable elastic arms toward the other end of the opening in the case opposite these protruding barriers, the arms turning toward the bottom plate along with the insertion of the battery and pressing the peripheral face of the battery toward the peripheral wall.
According to a second aspect of the invention, there are formed, toward one end of the peripheral wall where the battery holding section is formed, the first terminal pressing the battery toward the opposite part of the peripheral wall by being in contact with the peripheral face of the battery and, toward the other opposite end of the peripheral wall, the second terminal pressing the battery toward the protruding barriers provided toward the top face of the opening of the case by being in contact with one face of the battery, wherein the peripheral face of the inserted battery is pressed by the pressures of both the elastic arms and the first terminal toward the opposite part of the peripheral wall where the protruding barriers are formed.
According to a third aspect of the invention, the elastic arms are formed of hinges integrally extending from the peripheral wall of the case, and the battery holding section is rotatably held by the peripheral wall of the case via the elastic arms.
According to a fourth aspect of the invention, the battery holding section has a receptacle at the center of which the battery is to be inserted and pinches, opposite each other with this receptacle in-between, for pinching the battery, wherein a slope for preventing the battery from being inserted any farther, when it is inserted in the wrong direction, by being in contact with an edge of the top face of the battery is provided in the lower part within the pinches formed toward the bottom face.
According to a fifth aspect of the invention, the diameter of the hollow part of a virtual circle which is the trajectory of a tip of the slope toward the bottom face and tips of the protruding barriers is smaller than the external diameter of the battery.